Method of making an arched endless belt and belt made employing the method

ABSTRACT

A method of making an arched endless belt and belt made employing the method are provided wherein the method comprises the steps of disposing in tubular form a plurality of uncured belt-defining layers with the layers being adapted to define corresponding sections of the belt and curing the layers in a controlled environment to define the belt having a longitudinal axis and an arched configuration relative to the axis wherein prior to the disposing step the method comprises wrapping a shaping material consisting of an uncured gum material around a belt building device and the disposing step comprises wrapping the plurality of layers against the shaping material so that during the curing step the shaping material and controlled environment cooperate to define the arched configuration of the belt including all of its layers and during the curing step the shaping material is bonded to the layers and comprises an inner portion of the belt with the cured gum shaping material serving as a crack barrier for such inner portion.

This is a division of application Ser. No. 232,326, filed Feb. 6, 1981,now Pat. No. 4,443,281, issued Apr. 17, 1984.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of making a polymeric arched endlesspower transmission belt and to a belt made employing such method.

2. Prior Art Statement

In applications where a polymeric endless power transmission belt isoperated under comparatively high operating load it is important thatsuch belt have substantial stiffness or rigidity transverse itslongitudinal axis to assure that such belt does not "dish" or isstressed into a downwardly bowed configuration under load. This dishingresults in abnormally high stresses in the edge cords of the beltcausing breaking thereof and premature failure of such cords and theoverall belt. Dishing also causes high heat buildup within elastomericportions of the belt and this heat buildup degrades the adhesive bondbetween belt components as well as degrading the components themselvesresulting in premature failure. There is also a tendancy for such ahighly loaded belt to be subjected to unusually high stresses in theouter portion of its compression section, especially when operatingaround sheaves of comparatively small diameter, and such stresses causecracks which propagate into the body of the belt causing belt failure.

It is known in the art to provide a method of making a polymeric archedendless power transmission belt with the method comprising the steps ofdisposing in tubular form a plurality of uncured belt-defining layerswherein the layers are adapted to define corresponding sections of thebelt and curing the layers in a controlled environment to define thebelt having an arched configuration and as disclosed in U.S. Pat. No.4,019,399 and wherein the arched configuration is for the purpose ofminimizing dishing.

It is also known to provide a method of making an endless powertransmission belt which utilizes randomly arranged elongate fibers whichare disposed substantially perpendicular to the longitudinal axis of thebelt to increase the transverse or lateral stiffness of the belt and asdisclosed in U.S. Pat. No. 3,416,383 for a typical V-belt of trapezoidalcross section. A so-called central neutral axis belt is disclosed inU.S. Pat. No. 3,987,684 which uses fiber-loaded layers coperating withfabric layers to increase its transverse rigidity.

It is also known to provide a method of making a toothed belt ofsubstantially trapezoidal cross-sectional configuration which has theusual compression section and wherein the outer portion of thecompression section has a toothed configuration which is provided with aresilient compound between the teeth thereof. The resilient compound issofter than the rest of the belt and is used for providing an increasedtraction area and forming a yielding surface which also reduces noise;as disclosed in U.S. Pat. No. 2,062,568.

Finally, it is known in the art to provide a method of making acomparatively high load capacity endless power transmission belt whichemploys stress-relief slits in its compression section as disclosed inU.S. Pat. No. 3,995,507, for the purpose of avoiding high stresses andcracks in the compression section and overall belt.

It is an object of this invention to provide an improved method ofmaking a polymeric arched endless power transmission belt.

It is another object of this invention to provide an improved belt.

Other aspects, embodiments, objects, and advantages of this inventionwill become apparent from the following specification, claims, anddrawings.

SUMMARY

In accordance with the present invention there is provided an improvedmethod of making a polymeric arched endless power transmission beltwhich has minimum tendency to dish or crack in the manner mentionedabove, when subjected to high operating loads. The method of thisinvention comprises the steps of disposing in tubular form a pluralityof uncured belt-defining layers with the layers being adapted to definecorresponding sections of the belt and curing the layers in a controlledenvironment to define the belt having a longitudinal axis and an archedconfiguration relative to the axis.

In accordance with one embodiment of the invention, the improved methodcomprises the steps of providing a belt building device and wrappingshaping means made of an uncured gum material around the belt buildingdevice and the disposing step comprises wrapping the plurality of layersagainst the shaping means so that during the curing step the shapingmeans and controlled environment cooperate to define the archedconfiguration of the belt including all of the layers with the shapingmeans being bonded to the layers and cured therewith during such curingstep and comprising the inner portion of the belt, and the cured gumshaping means serving as a crack barrier for the inner portion of thebelt thus defined.

In accordance with another embodiment of this invention there isprovided a method of making a plurality of polymeric raw edged endlesspower transmission belts comprising the steps of disposing in tubularform a plurality of uncured belt-defining layers around a belt buildingdrum with the layers being adapted to define corresponding sections ofthe belts, curing the layers in a controlled environment to define abelt sleeve, cooling the sleeve, and cutting the sleeve to define theraw edged belts wherein the belts are made in the form of arched beltsdue to the method employing the further steps of wrapping a plurality ofshaping means made of an uncured gum material around the belt buildingdrum prior to the disposing step with the plurality of shaping meanscooperating with the controlled environment during the curing step todefine a corresponding plurality of integral axially spaced arched beltdefining portions in the layers and sleeve, each associated shapingmeans being bonded to the layers during the curing step and defining theinner portion of an associated arched belt defining portion and with thecutting step comprising cutting the sleeve on opposite sides ofassociated shaping means to define an associated arched belttherebetween and wherein the cured gum shaping means serves as a crackbarrier for the inner portion of its associated arched belt.

Also provided in accordance with this invention is an improved archedbelt made employing the method of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show present preferred embodiments of thisinvention, in which

FIG. 1 is an isometric view with parts in elevation, parts in crosssection, and parts broken away illustrating one exemplary embodiment ofa belt made utilizing the method of this invention;

FIG. 2 is a fragmentary isometric view illustrating initial method stepsemployed in making the belt of FIG. 1 and comprising wrapping fabricmeans about a toothed belt building drum followed by wrapping shapingmeans around the drum and fabric;

FIG. 3 is a fragmentary view with parts in elevation and parts in crosssection illustrating method steps of disposing in tubular form aplurality of uncured belt defining layers around the drum, fabric layer,and shaping means as wrapped in FIG. 2;

FIG. 4 is a cross-sectional view taken essentially on line 4-4 of FIG.3;

FIG. 5 is a schematic view illustrating the steps of curing the uncuredbelt defining layers of FIG. 4 to define a belt sleeve and the coolingof such sleeve;

FIG. 6 is a fragmentary view with parts in cross section and parts inelevation particularly illustrating the belt sleeve after curing andcooling thereof;

FIG. 7 is a fragmentary cross-sectional view taken essentially on theline 7--7 of FIG. 6;

FIG. 8 is a view similar to FIG. 7 taken on the line 8--8 of FIG. 6;

FIG. 9 is a view illustrating the step of cutting the cured and cooledbelt sleeve of FIGS. 6-8 to define a plurality of arched raw-edgedendless power transmission belts of FIG. 1;

FIG. 9A is a view similar to the lower portion of FIG. 2 illustratingshaping means provided with reinforcing fibers;

FIG. 10 is a view similar to FIG. 2 illustrating a modification of theshaping means in the form of a plurality of strips of uncured gummaterial;

FIG. 11 is a view similar to FIG. 1 illustrating another exemplaryembodiment of a belt made utilizing the method of this invention;

FIG. 12 is a view similar to FIG. 2 illustrating initial method steps indefining the belt of FIG. 11;

FIG. 13 is a view similar to FIG. 12 illustrating two modifications ofbelt shaping means which may be employed in modified method steps todefine the same belt sleeve and the making of another embodiment of thebelt of this invention; and

FIG. 14 is a fragmentary view with parts in elevation, parts in crosssection, and parts broken away illustrating certain steps of amodification of the method of this invention.

DETAILED DESCRIPTION

Reference is now made to FIG. 1 of the drawings which illustrates oneexemplary embodiment of an endless power transmission belt madeutilizing the method of this invention and wherein such belt isdesignated generally by the reference numeral 20. The belt 20 is madeprimarily of polymeric material and comprises a tension section 21, aload-carrying section 22, and a compression section 23, with the belthaving a longitudinal axis 24 and its sections disposed in an arch-likeor arched configuration relative to the axis 24 and as will be readilyapparent from FIG. 1. The belt 20 also comprises a strip 25 ofcomparatively soft gum material which comprises the outer portion of itscompression section, and the strip 25 will be described in more detailsubsequently.

The belt 20 has a toothed inner portion defined by alternatingprojections 26 and recesses 27 which define the outer portion of itscompression section 23 whereby the belt has longitudinal flexibilitywhich approaches the longitudinal flexibility of a conventional toothedbelt; however, the belt 20 has optimum transverse rigidity due to itsarched configuration, as seen in FIG. 1, which shows the belt sections21-23 in an arched configuration whereby the top surface 29 of the beltis disposed in a circular segment having a radius 30.

The strip 25 of gum material is a strip of gum rubber of a type commonlyused in the art and such strip serves as stress-relief means and a crackbarrier for the compression section 23 and hence the entire belt 20. Thegum material was employed during the manufacture of a belt sleeve fromwhich the the belt 20 is cut to define the arched configuration of suchbelt.

The gum material 25 preferably has a hardness which is substantiallyless than the hardness of the remaining portions of the belt 20 and suchhardness ranges between 35 and 80 as measured on the A scale of thecommonly used Shore Durometer. The gum material 25 when viewed at anycross section perpendicular to the longitudinal axis 24 of the belt hasa substantially plano-convex-sectional appearance defined by a planar orstraight bottom portion 31 and a convex top portion 32 which is convextoward the interior of the belt 20.

The belt 20 is a typical toothed belt of substantially trapezoidalcross-sectional configuration and has non-parallel sides or side walls33 which are symmetrically arranged about the axis 24. The straightouter or bottom portion 31 of the strip 25 extends between and adjoinsside walls 33 at its opposite ends. The belt sections 21, 22, and 23 aresuitably bonded together as a unitary mass and may be comprised ofvarious materials and component portions, as is known in the art ofmaking endless power transmission belts, and such sections will now bedescribed in more detail.

The tension section 21 has an inner rubber impregnated fabric layer 34and an outer rubber impregnated fabric layer 35. A polymeric or rubbermatrix material 36 is disposed between the layers 34 and 35 and therubber matrix 36 (FIG. 3) has randomly arranged elongate fibers 37disposed therein substantially perpendicular to the longitudinal axis24.

The load-carrying section 22 is comprised of a helically woundload-carrying cord 40 which is substantially centrally disposed within agum material 41 in the form of gum cushions which sandwich the cord 40therebetween, as is known in the art. The cord 40 may be made of one ormore filaments of a high-strength load-carrying material.

The compression section 23 is comprised of an inner fabric layer 43followed by a polymeric or rubber matrix material 44, the strip 25, anda fabric layer 45 bonded against the outside planar surface 31 of thestrip 25. The fabric layers 43 and 45 are preferably polymer or rubberimpregnated layers. The matrix material 44 of the compression section 23also has a plurality of randomly arranged elongate fibers embeddedtherein and such fibers are also disposed substantially perpendicular tothe longitudinal axis 24 of the belt and will also be designated by thesame reference numeral 37 as the fibers 37 of the tension section 21.

The fibers 37 of the tension section 21 and compression section 23 aredisposed in substantially parallel relation, as previously mentioned;and, such fibers 37 are disposed in an arched configurationcorresponding to the arched configuration of each belt section. Thefibers 37 were formed into their arched configuration by the gummaterial 25 during the manufacture of the belt sleeve S (FIGS. 6-8) fromwhich the belt 20 was cut. The fibers 37 may be made of suitable fibrousmaterials utilized in the art of making endless power transmissionbelts, including organic materials, and such fibers may have diametersranging between 0.001 inch and 0.050 inch and lengths ranging between0.001 inch and several inches.

The belt 20 may be made utilizing the method of this invention and aswill now be described with particular reference being made to FIGS. 2through 9 of the drawings. In particular, the method comprises the stepsof disposing in tubular form a plurality of uncured belt defining layers46 (FIG. 3) around a belt building drum 47. The uncured layers 46 arecomprised of compression section defining layers 23, load-carryingsection defining layers 22, and tension section defining layers 21. Thevarious uncured belt section defining layers of FIG. 3 have beendesignated by the same reference numerals 23, 22, and 21 as thecorresponding sections of the completed belt 20, and this has been donefor ease of description and understanding of the invention. The buildingdrum 47, about which the layers 46 are disposed, has an outer portionmade of a polymeric material in the form of a suitable synthetic plasticmaterial 50 and an inner portion 51 made of metal.

The exemplary method disclosed herein comprises the steps of coveringthe building drum 47 with a rubber impregnated fabric layer 45 followedby wrapping the fabric layer 45 with a plurality of shaping means ofuncured gum material and each also designated by the same referencenumeral 25 as the cured gum material 25 in the completed belt 20. Thefabric 45 and uncured gum 25 are wrapped around the building drum 47prior to disposing in tubular form the remaining uncured compressionsection defining layers 23 and uncured belt section defining layers 22and 21.

The uncured shaping means 25 are provided as an uncured sheet-likestructure of gum material which is designated generally by the referencenumeral 52; and, such shaping means 25 are defined as an integral partof and in parallel relation across such structure, as will be readilyapparent from FIG. 2. The shaping means 25 are interconnected byintegral interconnecting portions 53 of the sheetlike structure.

As seen in FIG. 2 of the drawings, the building drum 47 has a pluralityof alternating axial projections 54 and recesses 55 disposedcircumferentially therearound in parallel relation and parallel to acentral axis 56 of the building drum 47. The projections 54 and recesses55 cooperate to define corresponding recesses 27 and projections 26respectively in a cured belt sleeve S (FIG. 6).

The uncured belt defining layers 46 are disposed in position about thedrum 47 as shown in FIGS. 2, 3, and 4. The layers, as illustrated inFIGS. 3 and 4, are then suitably cured in a controlled environmentprovided by a conventional curing device 59 which is illustratedschematically in FIG. 5 to define the cured belt sleeve S. The curingdevice 59 may utilize steam at controlled temperatures and pressures andsuch steam may be circulated both internally and externally of thebuilding drum 47, as is known in the art, to cure the uncured layers 46and define the belt sleeve S of FIG. 6.

The sleeve S is then suitable cooled in a cooling device 56, which isalso illustrated schematically in FIG. 5. The cooling device 56 may beany device used in the art for cooling a cured belt sleeve S.

The belt sleeve S is cut utilizing suitable cutting devices or cutters57 as illustrated in FIG. 9. The cutting action is preferably achievedwith the sleeve S disposed on its building drum 47 while supporting suchdrum on centers as is known in the art.

The sleeve S has a toothed inner portion defined by the toothedcompression section defining portion of such sleeve whereby in order tocut such sleeve on the drum 47 it is necessary to cut through the outerpolymeric or synthetic plastic portion 50 of the building drum 47. Tofacilitate this cutting, portion 50 is made of a material which iseasily cut yet is capable of withstanding the temperatures and pressuresencountered during curing and cooling. However, once the cutting actionis complete, the plastic portion 50 is stripped from the outside of thedrum 47 and a new outer portion is disposed around the metal portion 51of such building drum in preparation for disposing in tubular formanother plurality of uncured belt defining layers after wrapping shapingmeans of the uncured gum material in position to enable defining anotherbelt sleeve similar to belt sleeve S of FIG. 6.

During the cutting utilizing the cutters 57 it will be appreciated thatsubstantially triangular or wedge-like portions 60 of the belt sleeve Sare cut away. Each wedgelike portion 60 is shown disposed between cutlines, represented by dot-dash lines 61, defined by the cutters 57.Further, each arched belt 20 cut from sleeve S is a toothed belt havingan undulating inside surface defined by alternating projections 26 and27 in the outer portion of the compression section.

The shaping means, i.e., cured gum 25, at any desired locationthroughout the entire axial length of the arched belt 20 is ofsubstantially uniform transverse cross section and of plano-convexconfiguration, as described earlier. This will be readily apparent fromFIG. 7 which shows a cross section of the belt sleeve S, and of belts 20between cut lines 61, at cross sections through axially aligned beltapexes or projections 26 while FIG. 8 shows a similar cross section ofthe belt sleeve S, and of belts 20 between cut lines 61, at crosssections through axially aligned belt recesses 27 at the lowest pointsof such recesses.

Thus, it is seen that the plurality of shaping means or uncured stripsof gum rubber 25 cooperate with the controlled environment of the beltcuring device 59 during the curing step of FIG. 5 to define a pluralityof integral axially spaced arched belt defining portions of the layersand sleeve S and as illustrated in FIGS. 7 and 8. Each arched beltdefining portion has also been designated by the reference numeral 20(between its cut lines 61) even though such portions have not been cutby cutters 57 as illustrated in FIG. 9.

The cutting step (FIG. 9) comprises cutting the sleeve S, with cutters57, on opposite sides of an associated shaping means or shaping strip 25to define the associated arched belt 20 therebetween; and, it will beappreciated that each associated shaping means 25 is bonded to itsassociated layers during the curing step and defines the inner portionof an associated arched belt defining portion 20. The cured gum shapingmeans 25 serves to define the arched belt 20 which has optimumtransverse rigidity as well as longitudinal flexibility. In addition,the gum material utilized to define the arched configuration of the beltserves as a crack barrier for the inner portion of the belt 20.

The method of this invention has been described as using shaping meansconsisting of a sheet-like structure 52 having the plurality of shapingmeans 25 defined as an integral part thereof with interconnectingportions 53 of the sheet-like structure therebetween. However, suchshaping means 25 may be as provided in FIG. 10 of the drawings whichillustrates shaping means comprised of a plurality of separate uncuredshaping strips of gum rubber which are disposed in spaced relationaxially along the building drum 47 with each strip extendingcircumferentially around such building drum. It will be appreciated thatthe technique illustrated in FIG. 10 merely requires that the individualshaping strips 25 be suitably positioned in equally spaced apartrelation as indicated by the typical spacing 63 therebetween and thespacing 63 may be substantially equal to the width 64 of theinterconnecting portions 53 of the sheet-like structure 52 whereby thebelts 20 defined using the strips 25 of FIG. 10 would be substantiallyidentical to the previously described belts 20.

Nevertheless, regardless of whether the shaping means is in the form ofa sheet-like structure, as shown in FIG. 2, or a plurality o separatestrips, as shown in FIG. 10, the opposite ends of each shaping means 25is suitably disposed in abutting relation or joined on a bevel orsuitable joint so that each cured shaping means or gum portion 25 has acontinuous and substantially uniform cross section throughout itsendless path whereby each component 25 may serve its dual purpose ofshaping means and crack barrier in a reliable manner.

Having described the belt 20 and method of making same wherein such beltis in the form of a toothed belt, i.e., having a toothed compressionsection, reference is now made to FIGS. 11 and 12 of the drawings whichillustrate a similar arched belt and method steps in making samerespectively wherein the belt is free of teeth and the belt is of theusual trapezoidal cross-sectional configuration having an archedconfiguration similar to the arched configuration illustrated in FIG. 2.Except for the absence of a toothed compression section, the belt ofFIG. 11 is substantially identical to the belt 20 of FIG. 1; therefore,the belt of FIG. 11 will be designated by the general reference numeral20A and its tension section, load-carrying section, and compressionsection will be designated by the reference numerals 21A, 22A, and 23Arespectively.

In a similar manner, as described in connection with the belt 20, eachbelt 20A has a shaping means in the form of a gum strip 25A defining theouter portion of its compression section 23A with the gum materialhaving been used during the manufacture of the belt sleeve from whichthe belt was cut to define the arched configuration in such belt 20A.The gum material has similar properties as previously described and itwill be seen that the various sections 21A, 22A and 23A aresubstantially identical and similar to previously described sections.

The tension section 21A and compression section 23A of belt 20A alsohave randomly arranged elongate fibers 37A embedded therein and disposedperpendicular to the longitudinal axis 24A of the belt 20A. The fibers37A are also disposed in substantially parallel relation and in anarched configuration corresponding to the arched configuration of itssections in a similar manner as described for the belt 20. Further, thefibers 37A may be substantially identical to the previously describedfibers and thus will not be described again.

The only difference in the method of making the belts 20A and the belts20 is that in making the belts 20A a plain building drum 67 (FIG. 12) isused instead of a toothed drum. Accordingly, the drum 67 is free ofteeth and employs an outer polymeric portion 70 made of a plasticmaterial, or the like, and an inner portion comprised of a metallicmaterial 71. The fabric material 45A is wrapped around the drum 67followed by sheet-like structure 52A having shaping means 25A defined asan integral part thereof. As described for the belts 20, the beltdefining layers may then be wrapped in position in a similar manner asillustrated in FIGS. 3 and 4, followed by curing and cooling as shown inFIG. 5, and cutting as shown in FIG. 9 to define a plurality of beltsidentical to the belt 20A of FIG. 11.

During the cutting of the belt sleeve to define either of the belts 20or 20A it will be appreciated that the cutting is preferably achievedwith the sleeve S on its building mandrel or drum either 47 or 67. Inthis manner it is a simple procedure to move the cutters 57 across theaxial length of the sleeve S and define each belt either 20 or 20A sothat shaping mens defined by the rubber gum material is symmetricallyarranged and precisely located in its belt. In particular, with thissymmetrical arrangement the inwardly or upwardly convex surface 32 and32A of the gum material of each belt 20 and 20A respectively is disposedwith its apex coplanar with a plane bisecting a transverse cross sectionthrough the belt. However, it will be appreciated that, if desired, thetoothed belt sleeve S illustrated in FIG. 6 or the plain belt sleevedefined in the process of defining a plurality of belts 20A, may in eachinstance be stripped from its associated mandrel and then supported on acutting mandrel, as is known in the art, and the cutting of the sleevecan also be achieved with precision inasmuch as shaping means of gummaterial in each instance is precisely located along the axial length ofthe sleeve.

The belt defining sleeve S has an undulating outside surface asillustrated in FIGS. 7, 8, and 9 which is defined by the shaping means25 or 25A. This undulating outside surface aids in the cutting of thecured and cooled sleeve S using cutters 57.

In this disclosure of the invention various sections of each belt 20 and20A are shown defined in a particular specific configuration utilizing aparticular sequence of fabric layers, rubber impregnated layers,fiber-loaded layers, etc; however, it will be appreciated that themethod of this invention may be utilized in defining arched beltswherein the various layers may be in any desired sequence, or anydesired material or combination of materials, as is known in the art.

In this disclosure of the invention each shaping means, such as shapingmeans 25, whether provvided in the form of the sheet-like structure ofFIG. 2 or separate strips as shown in FIG. 10, are illustrated anddescribed as having a straight outer surface 31 and an inwardly convexinner surface 32. However, it will be appreciated that such shapingmeans may have other cross-sectional configurations. To highlight thispoint, FIG. 13 has been presented and illustrates a fragmentary portionof a belt building drum similar to the drum 67 of FIG. 12 with a singleshaping strip 72 at one end portion thereof and a sheet-like structure73 at the opposite end portion thereof which has integral shaping means72. Each shaping means or strip 72 is of substantially rectangularcross-sectional configuration and the rectangular configuration of eachshaping means is disposed symmetrically within an associated belt todefine the arched configuration therein, including all componentportions or sections of the belt and including any stiffening fibersdefined in one or more sections of such belt thus defined. However, itis to be understood that in using a rectangular strip, such strip wouldnot extend across the full width of the compression section, otherwisean arched configuration would not result. Instead, the rectangular stripwould extend across only from about 1/2 to 2/3 of the full width of theouter portion of the compression section while being centrally andsymmetrically disposed therein whereby with this construction the beltdefining layers would, in essence, bow or bend around the rectangularshaping means or strip 25 during curing to define an associated archedbelt.

The method of this invention has been illustrated and described inconnection with the making of a plurality of belts by forming a beltsleeve S and cutting such sleeve to define a plurality of arched endlesspower transmission belts. However, it will be appreciated that belts maybe made individually as illustrated in the method of FIG. 14 of thedrawings.

In particular, the modified method of FIG. 14 comprises the steps ofdisposing in tubular form a plurality of belt defining layers similar tothe layers previously described and such layers will be designated bythe reference numerals 23, 22, and 21 and define the compressionsection, load-carrying, and tension section defining layersrespectively. As previously described, the layers are adapted to definecorresponding sections of the belt 20 therefrom. The layers are cured ina controlled environment and in particular are cured utilizing a moldstructure 74 to define the belt having alongitudinal axis and an archedconfiguration relative to the axis.

The belt building means of the mold device 74 comprises an innerbuilding means in the form of a building ring 75 and shaping means 25made of an uncured gum material which is disposed around the ring 75after disposing of the fabric layer 45 in position. The belt defininglayers 23, 22, and 21 are then wrapped against the shaping means 25whereupon mold device 74 is suitably closed by suitably attaching themold sides 76 in position to confine the belt body. The outer portion ofthe mold device is exposed or shown at 77 whereby the shaping means 25and layers 23, 22, and 21 are subjected to a controlled curingenvironment similar to the steam pressure provided by the curing device56. During curing, the shaping means 25 and the controlled pressuresprovided by the steam environment cooperate to define the archedconfiguration in the belt including all of its layers, and it will beappreciated that the shaping means or uncured shaping strip 25 is bondedto the layers and defines the inner portion of the belt thus made. In asimilar manner as described earlier, the belt 20 of FIG. 14 has the gummaterial of the shaping means 25 which serves as a crack barrier for theinner portion of such belt.

The belt 20 defined, as shown in FIG. 14, is a toothed belt inasmuch asthe ring 75 has outer teeth therein, and the non-parallel side walls 33thereof are finished sides as produced by the corresponding surfaces 78of the mold sides 76. Further, it will be appreciated that the moldingring 75 defines the toothed inner portion of the belt 20.

However, it is to be understood that the method basically illustrated inFIG. 14 for defining a single belt 20 may be employed in defining a beltsimilar to the belt 20A wherein the ring 75 would be a plain ring havinga plain right circular cylindrical outside surface. It will also beappreciated that a rectangular strip similar to the rectangular stripillustrated in FIG. 13 may be utilized to make the belt of FIG. 14provided that such a rectangular strip would be substantially narrowerin width than the outer portion of its compression section, and aspreviously presented.

The fibers 37 provided in the tension section and compression section ofeach belt described herein are essentially as previously described. Inpracticing the method of this invention a plurality of such fibers arerandomly disposed in spaced parallel relation in a sheet of anassociated uncured matrix material and such matrix material may then bedisposed so that the fibers 37 thereof are substantially parallel to thelongitudinal or central axis to its associated building drum or ring.For example, in the belt 20, the fibers 37 are disposed in associateduncured rubber matrix material 36 and 44 of the tension and compressionsections respectively. Once the sleeve, with the fibers 37 thus disposedis cured, the fibers are bowed to define an arch-like path or archedconfiguration corresponding to the arched configuration of the beltsections and overall belt.

Reference is now made to FIG. 9A of the drawings which illustrates anexemplary modification of uncured shaping means which is designatedgenerally by the reference numeral 25M and disposed around a buildingdrum 47 of the type described earlier. The shaping means 25M areprovided as an integral part of an uncured sheet-like structure 52M ofpolymeric material; and, the shaping means 25M are disposed in parallelrelation across the structure 52M and such shaping means areinterconnected by integral interconnecting portions 53M of thesheet-like structure. The shaping means 25M may be used in the method ofthis invention and in defining the belt of this invention essentially asdescribed previously whereby the previous description will not berepeated.

The main difference between the shaping means 25M and shaping means 25is that the shaping means 25M utilizes a plurality of fibers which aredisposed therein and such fibers are designated by the reference numeral37M. The fibers 37M are randomly disposed in substantially parallelrelation and substantially perpendicular to the longitudinal axis of theshaping means 25M and hence the longitudinal axis of its associatedbelt. As in the case of the fibers 37 previously described, the fibers37M may be made of any suitable fibrous material utilized in the art ofmaking endless power transmission belts. Further, the fibers 37M mayhave diameters and lengths essentially as described previously for thefibers 37.

The fibers 37M provide improved support for the polymeric matrix portionof the uncured shaping means 25M. For example, the fibers 37M, by theirtensile stiffness in the fiber direction contribute to the stability ofthe arched configuration of the shaping means 25M.

Fibers 37M have only been illustrated and described in connection withthe uncured shaping means 25M which are defined as an integral part ofthe sheet-like structure 52M which has integral interconnecting portions53M. However, it is to be understood that the uncured shaping means 25and 72 of the types illustrated in FIGS. 10 and 13 respectively may alsobe provided with fibers 37M and for the same reasons as describedearlier. In addition, the reinforcing fibers 37M may be provided in theuncured shaping means of FIG. 12 utilized in making the belt of FIG. 11.

The matrix material defining the shaping means 25M is also preferablymade of an uncured gum material and after curing such gum material has ahardness within the range previously described for the gum material 25.Further, although the cured gum shaping means 25M serves as a crackbarrier for the inner portion of its associated arched belt, the fibers37M in the cured shaping means also serve as reinforcement and tend toprevent any cracks that might develop in the compression section of thebelt from enlarging in size or propagating toward the central portion ofsuch belt.

In this disclosure, the various components of the belt have beenillustrated by cross-hatching in the drawings as being made of rubber;however, it is to be understood that any suitable polymeric materialemployed in the art of making power transmission belts may be usedinstead of rubber, if desired. Further, although the uncured shapingmeans 25, 72, and 25M have been described as being preferably made ofuncured gum material, such as gum rubber, it is to be understood thatany suitable polymeric material, e.g., synthetic plastic, or the like,may be used to define such shaping means provided it is capable ofproviding the functions described herein.

Certain fabric layers have also been described herein as being rubberimpregnated fabric layers. Accordingly, one or both surfaces of asuitable fabric material may be impregnated with rubber utilizing anysuitable technique known in the art. Further, the fabric material may bewoven fabric, non-woven fabric, knitted fabric, or any other fabriccapable of being used in the art of making endless power transmissionbelts.

While present exemplary embodiments of this invention, and methods ofpracticing the same, have been illustrated and described, it will berecognized that this invention may be otherwise variously embodied andpracticed within the scope of the following claims.

What is claimed is:
 1. In an endless power transmission belt madeprimarily of polymeric material and comprising a tension section havingan outer layer, a load carrying section, and a compression sectionhaving an outside surface, said belt having a longitudinal axis and itssections disposed in an arched configuration relative to said axis, theimprovement comprising; a strip of comparatively soft gum materialhaving an inwardly convex inner surface and a planar outer surfacedefining an outer portion of said compression section; said gum materialserving as a crack barrier for said compression section and belt, andsaid gum material providing a base for said arched configuration of saidtension, load carrying and compression sections.
 2. A belt as set forthin claim 1 in which said gum material has a hardness ranging between 35and 80 when measured on the A scale of a Shore Durometer.
 3. A belt asset forth in claim 2 in which said gum material is a rubber compound. 4.A belt as set forth in claim 3 and further comprising a fabric layerdefining the outer layer of said tension section and a fabric layerbonded against said gum material and defining the outside surface ofsaid compression section.
 5. A belt as set forth in claim 1 in whichsaid gum material when viewed at any cross section perpendicular to saidlongitudinal axis has a straight outer surface and an inwardly convexinner surface thereby defining a substantially plano-convexcross-sectional appearance.
 6. A belt as set forth in claim 5 in whichsaid belt has non-parallel side walls and said straight outer surfaceextends between and adjoins said side walls at its opposite ends.
 7. Abelt as set forth in claim 6 in which at least one of said sections hasrandomly arranged elongated fibers therein disposed perpendicular tosaid longitudinal axis, said fibers also being disposed in substantiallyparallel relation and in an arched configuration corresponding to thearched configuration of its section, said fibers having been disposed intheir arched configuration by said gum material during said manufactureof said belt.
 8. A belt as set forth in claim 7 in which saidcompression section has a plain outer portion which is free ofundulations.
 9. A belt as set forth in claim 7 in which said compressionsection has a toothed outer portion defined by alternating projectionsand recesses thereby defining an undulating outer surface in saidtoothed outer portion.
 10. A belt as set forth in claim 7 in which saidpolymeric material of said belt is rubber material and another of saidsections also has randomly arranged elongate fibers therein disposedperpendicular to said longitudinal axis, said fibers of said othersection also being disposed in substantially parallel relation and in anarched configuration corresponding to the arched configuration of itssection, said fibers of said other section also having been disposed intheir arched configuration by said gum material during said manufactureof said belt.
 11. A belt as set forth in claim 1 in which said gummaterial has a plurality of randomly arranged elongate fibers embeddedtherein substantially in parallel ralation and substantiallyperpendicular to said longitudinal axis, said fibers serving asreinforcement for said crack barrier and tending to prevent any cracksthat might develop in the compression section of said belt fromenlarging in size and propagating toward the central portion of saidbelt.